Method of producing an electrically charged film

ABSTRACT

A method of producing an electrically charged film includes the steps of forming a molten thermoplastic material into a web, electrically charging the web while the web is at a temperature substantially at or above a solidification temperature thereof, cooling the web below the solidification temperature thereof after charging and winding the web into individual rolls immediately following the cooling step.

TECHNICAL FIELD

The present invention relates generally to film products, and moreparticularly to a method of producing an electrically charged film.

BACKGROUND ART

A web or sheet of material is often used to protect a surface and/or oneor more items that may be disposed on the web or sheet. For example,paper has been used for many years to line shelves, drawers and othersurfaces of articles. The paper may be plain (i.e., uncoated), coatedand/or adhesive-backed. Paper or other material has also been used asplacemats or as a table covering.

Another example of the use of a web or sheet is as a protective coveringon other, larger structures, such as a dropcloth on a floor or a linerin a trunk of a car or on a bed of a truck. These products typicallymust be sufficiently durable to withstand foot traffic and/or otherforms of abuse, although less durable materials (e.g., paper) may beused as temporary protective coverings.

Mix U.S. Pat. No. 1,151,895 discloses a sanitary kneading board whereina quantity of parchment paper is unwound from a roll and placed atop theboard to completely cover the surface thereof. Similar arrangements aredisclosed in Johnson U.S. Pat. No. 1,952,375 and Hoel U.S. Pat. No.2,369,898, although the wax paper is used instead of parchment paper inthe latter.

Pollock U.S. Pat. No. 5,193,793 discloses a mixing board wherein aplurality of stacked plastic sheets are disposed on a top surfacethereof. Each of the plastic sheets has a backing of pressure sensitiveadhesive binding the sheets together. A user may mix a compound on a topsheet and may thereafter peel off the top sheet and dispose of same sothat a clean surface is provided for subsequent use.

A number of arrangements have been developed wherein anelectrostatically charged sheet is used to secure an article to asurface. For example, Henley U.S. Pat. No. 5,970,638 discloses atransparent electrostatic vinyl sheet and a cover film wherein anobject, such as a dried and pressed flower, is tightly sealed betweenthe vinyl sheet and the cover film to create a sealed ornament. Thesealed ornament may be applied to a non-porous surface and theelectrostatic film maintains the ornament in position thereon. Otherarrangements utilizing electrostatic sheets to mount objects aredisclosed in Arbisi U.S. Pat. No. 5,826,851, Baryla U.S. Pat. No.4,741,119, Saetre U.S. Pat. No. 5,102,171 and Rubino U.S. Pat. No.4,992,121.

Peck U.S. Pat. No. 5,899,010 discloses a reusable banner systemincluding a sheet of plastic material and a plurality of flexible staticcling vinyl indicia that may be placed on the sheet of plastic materialto form a message. The indicia are maintained in position on the sheetof plastic material by the electrostatic charge carried by the indicia.In an alternate embodiment, the sheet of plastic material carries anelectrostatic charge and the indicia are made of nonporous plastic.

Stonehouse U.S. Pat. No. 5,010,671 discloses a flip chart comprising atleast two sheets disposed in overlying relationship. The sheets areelectrically charged and are releasably securable to a surface by staticcling. The sheets are adapted for removable marking thereon by a feltpen and are retained on a backing board by staples. Each sheet may betorn from the staples to permit removal of the sheet from the flipchart.

Boyd U.S. Pat. No. 5,207,581 discloses a writing apparatus includingflexible electret film that is capable of being erasably written upon bya dry erase marker. The apparatus includes a roll of electret filmdisposed in a receptacle, brackets for mounting the receptacle to a wallor flip chart stand and a cutter for separating the film into sheets.

Cooledge et al. U.S. Pat. No. 5,258,214 discloses a thermoplastic filmmaterial having a preprinted image thereon and provided with a staticelectrical charge for securing the film to a surface. The material maybe packaged as sheets or in roll form with perforations to permitseparation thereof.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a method ofproducing an electrically charged film includes the steps of forming amolten thermoplastic material into a web, electrically charging the webwhile the web is at a temperature substantially at or above asolidification temperature thereof, cooling the web below thesolidification temperature thereof after charging and winding the webinto individual rolls immediately following the cooling step.

According to a further aspect of the present invention, a method ofproducing an electrically charged film includes the steps of extruding amolten thermoplastic material into a web, wherein the web includes asurface adapted for marking by a marking device, electrically chargingthe web while the web is at a temperature above a solidificationtemperature thereof and cooling the web below the solidificationtemperature thereof after charging. The web is thereafter wound intoindividual rolls immediately following the cooling step. The step ofcharging results in a web having a moderate to high resistance to shearforces but which can be readily peeled from a surface.

Other aspects and advantages of the present invention will becomeapparent upon consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 comprises an isometric view of a cutting board having a filmmaterial according to the present invention disposed thereon;

FIG. 1A comprises an isometric view of a support surface having a filmmaterial according to the present invention disposed thereon;

FIG. 2 comprises an isometric view of a container in combination with aroll of film material according to the present invention;

FIG. 3 comprises a plan view of a film according to the presentinvention with markings thereon created by a dry-erase marker;

FIG. 4 comprises an isometric view of a multilayer polymer filmaccording to the present invention;

FIGS. 5 and 6 comprise isometric views of shelves and a drawer,respectively, that are lined with a film material according to thepresent invention;

FIG. 7 is an isometric view of a film with a pouch containing a pad orother member impregnated with a substance;

FIG. 8 is a sectional view taken generally along the lines 8-8 of FIG.7;

FIG. 9 is a diagrammatic plan view of apparatus for charging and windingfilm material onto individual rolls;

FIG. 10 is an isometric view of a film material with a multi-compartmentstructure retained thereon; and

FIG. 11 is a sectional view taken generally along the lines 11-11 ofFIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, a film material 10 according to the presentinvention is illustrated. In accordance with the preferred embodiment,the film material 10 comprises a polymer or other material that isreadily capable of accepting and retaining an electric charge. Alsopreferably, the material is inexpensive so that it may be used once andrecycled or discarded. Still further, the film material 10 issufficiently durable to resist contact by a knife or other utensil andhas adequate resilience to resist cracking when flexed. Still further inaccordance with the preferred embodiment, the material comprises aplastic film that is liquid impermeable and preferably approved by theFDA for contact with food.

The thickness of the film material 10 is in a range encompassing up toapproximately 8 mils, with a range of approximately 0.5 to approximately5 mils being preferred, the range of approximately 1 to approximately 4mils being more preferred and the range of approximately 1.5 toapproximately 3 mils being most preferred. Further, the film material ispreferably charged by application of a positive or negative electricfield of at least approximately 15,000 volts thereto at an approximatedistance of between ½ inch and 1 inch, with at least approximately20,000 applied volts being more preferred and at least approximately30,000 applied volts being most preferred substantially at a distance of¾ inch. If desired, the material 10 may be exposed to a positiveelectric field on one side thereof and a negative electric field on theother side thereof wherein the magnitudes of the applied fields are asnoted above. In alternate embodiments, the film material 10 is exposedto the same polarity fields on opposite sides thereof (i.e., a firstside of the material 10 is exposed to a first positive field and asecond side of the material 10 is exposed to a second positive field orfirst and second sides of the material 10 are exposed to first andsecond negative fields, respectively.). In addition, the material 10preferably retains a charge sufficient to develop an electric field at avoltage substantially equal to at least approximately 1500 volts at aspecified time after charging of the material, such as three months ormore. More preferably, the material retains sufficient charge to developan electric field at a voltage of at least approximately 2500 volts, andmost preferably at least approximately 3500 volts, at least for theperiod of time between the initial application of charge to the filmmaterial 10 and the longest anticipated time to use by the consumer.

The film material 10 of FIG. 1 is placed atop a support surface 12,shown as a cutting board, and one or more items 14 are placed on anupper surface 15 of the film material 10 and are processed. As seen inFIG. 1A, if desired, the film material may instead be disposed on adifferent structure 13, such as a countertop, a table, a tray, etc . . .. Referring again to FIG. 1, in accordance with one embodiment, theitems 14 comprise food items that are cut with a knife 16 and/orotherwise manipulated (such as during mixing, kneading, chopping, andthe like) while on the film material 10. The film material 10 preventsthe transmission of juices and other materials released from the fooditem(s) 14, including bacteria, from the upper surface 15 to the supportsurface 12. The film material 10 also prevents the transmission ofmaterials and bacteria from the support surface 12 to the upper surface15 of the film material 10, and hence, contamination of the food item(s)14 is avoided. If desired, the film material 10 may optionally includeone or more antimicrobial and/or bactericidal components that limit germand/or bacterial activity on at least the upper surface 15.

The support surface is preferably of a suitable material andconstruction to provide static attraction with the film material 10.Ideally, the support surface provides sufficient support to the filmmaterial and the item(s) 14 to permit safe and efficient processingthereof. When processing of the food item(s) 14 is complete, the filmmay be removed from the support surface 12 and may be recycled ordisposed of, preferably after first folding and/or wadding the filmmaterial 12 in such a manner so as to capture food particles and juicestherein. Also preferably, the charge carried by the film material 10 isof a magnitude such that the film material 10 is restrained againstsignificant movement during processing of the item(s) 14 thereon, yeteasy release of the film material 10 from the support surface 12 can beaccomplished, when desired. Specifically, the film material 10preferably exhibits a moderate to high resistance to shear forces but arelatively lower resistance to a peeling force. Also, the resistance toshear forces is preferably not so great as to prevent any lateraladjustment of the position of the material 10 once it is placed on asurface. Thus, the material 10 can be placed on a surface and theposition thereof may be adjusted, and thereafter the material 10 isretained in position by the electrical charge carried by the material10. As a result, the material 10 can be written on or items can beprocessed and/or moved on the material 10 without substantial lateralmovement of the material 10, yet the material can be readilyrepositioned or peeled from the underlying surface, when desired.

The film material preferably comprises a monolayer or multilayerstructure of any suitable polymer material(s) formed into a film, suchas an olefin (e.g., polypropylene or polyethylene), nylon, PET, Teflon,or any other family of chemicals capable of being formed into a filmand/or may comprise non-oriented, oriented or biaxially orientedmaterials. The film alternatively may comprise combinations of suchmaterials in different layers that are coextruded or laminated orotherwise joined together.

In the preferred embodiment of the invention, the film material 10 isextruded into a web and wound onto one or more large master rolls. Thefilm material 10 is thereafter unwound from the master roll(s), passedthrough any commercially available electrostatic charging machine andimmediately thereafter formed into individual user rolls. Each roll issupplied to the end user, who preferably cuts or otherwise trims thematerial to a desired size and/or shape. As seen in FIG. 2, a roll 20 ofthe film material 10 is supplied in a box 22 or other container and acutter bar 24 is mounted on the box 22 to permit the user to trim thematerial 10 into a sheet of desired size. Alternatively, the material 10may be supplied to the end user as precut sheets in a box or othercontainer. Still further, the material 10 may be perforated to allow auser to easily tear the material 10 into sheets.

FIG. 9 illustrates the foregoing procedure in greater detail whereinfilm material 10 stored on a large master roll 21 is unwound therefromby a driven bed roller 23 and passed over a further roller 25 disposedadjacent a charging machine 26. Preferably, the charging machine 26comprises a Tetra charging bar sold by Simco of Hatfield, Pa., whichpreferably delivers a positive charge to the film material 10. Alsopreferably, the film material travels past the charging machine 26 at aline speed of approximately 800 feet per minute, although higher orlower travel speeds could alternatively be used. The charged filmmaterial 10 then passes over further rollers 27 a, 27 b and 27 c and iswound onto individual rolls carried by a rotatable turret 28.Preferably, the rollers 25, 27 a and 27 c are grounded to a machineframe by brushes or other devices and the rollers 27 a-27 c areinsulated by a Teflon coating. In addition, the roller 25 is preferablycoated by an electrically non-conductive industrial hard coating.

The foregoing manufacturing technique results in less handling bymanufacturing personnel, as compared to a technique wherein the extrudedfilm is wound onto a large master roll, and the master roll isthereafter electrostatically charged in bulk and the charged film isunwound from the master roll and wound onto individual rolls or formedinto individual sheets. This reduction in handling results in bettercharge retention and improved film quality. Also, the foregoingtechnique results in production of amounts of ozone that are withinacceptable limits.

If desired, the film material 10 may be charged while in the semi-moltenstate, thereby forming an electret having internal charges in the filmstructure. Specifically, this aspect of the present inventioncomprehends the steps of forming a molten thermoplastic material into aweb, electrically charging the web while the web is at a temperaturesubstantially at or above a solidification temperature thereof, coolingthe web below the solidification temperature thereof after charging andwinding the web into individual rolls immediately following the coolingstep. The web may be of single layer or multi-layer construction,wherein the latter may be accomplished by coextrusion techniques.Preferably, the method comprehends the use of a charging machine similaror identical to the charging machine 26 described above which is locateddownstream of an extrusion die that extrudes the thermoplastic web.After charging, the semi-molten material is allowed to cool, either byexposure to ambient conditions or by active chilling by a chiller roll.One or both outer surfaces of the web may be corona-treated to permitmarking by a marking device. Thereafter, the cooled web is preferablyimmediately rolled onto individual user rolls and packaged.

During charging, the material 10 is exposed to a positive or negativeelectric field preferably when the film temperature is just greater thanthe glass transition temperature T_(G) for the material 10. Alsopreferably, the semi-molten material is exposed to at leastapproximately 15,000-17,000 volts at an approximate distance of between½ inch and 1 inch, with at least approximately 20,000 applied voltsbeing more preferred and at least approximately 30,000 applied voltsbeing most preferred substantially at a distance of ¾ inch. If desired,the material 10 may be exposed to a positive electric field on one sidethereof and a negative electric field on the other side thereof whereinthe magnitudes of the applied fields are as noted above. In alternateembodiments, the film material 10 is exposed to the same polarity fieldson opposite sides thereof, i.e., a first side of the material 10 isexposed to a first positive field and a second side of the material 10is exposed to a second positive field or first and second sides of thematerial 10 are exposed to first and second negative fields,respectively.

This technique, as opposed to the electrostatic charging described abovethat creates surface charges in the material 10, results in a morestable retention of electric charge over time and with exposure toambient conditions. Also if desired, the film may initially be chargedwhen partially molten and thereafter may be passed through a chargingmachine after solidification of the material 10 just before winding intoindividual rolls as noted above to obtain a product with a combinationof internal and surface charges.

Regardless of whether the film is charged only when partially molten orcharged before and after solidification, the resulting film preferablyhas at least the electrical charge retention characteristics specifiedabove. That is, the resulting film material 10 preferably retains acharge sufficient to develop an electric field at a voltagesubstantially equal to at least approximately 1500 volts at a specifiedtime after charging of the material, such as three months or more. Morepreferably, the material 10 retains sufficient charge to develop anelectric field at a voltage of at least approximately 2500 volts, andmost preferably at least approximately 3500 volts, at least for theperiod of time between the initial application of charge to the filmmaterial 10 and the longest anticipated time to use by the consumer.

The film material 10 may be colorless or pigmented and may betransparent, translucent or opaque, as desired. Referring to FIG. 4,according to one embodiment, the material 10 may comprise a multilayercoextruded or laminated structure comprising a cavitated center layer 30of a polypropylene sold under the trademark OPPALYTE® by Exxon MobilCorp., first and second intermediate layers 32, 34 of polypropylenemodified by the addition of titanium dioxide thereto to obtain a whitepigmentation and top and bottom outer layers 36, 38. In this embodiment,the top outer layer 36 is preferably polypropylene that has beencorona-treated to allow marking with either a permanent marking deviceor to allow removable marking with a dry-erase marker. Further, thebottom outer layer 38 is preferably polypropylene modified by theaddition of any known material that facilitates cold sealing of the filmmaterial 10. If desired the bottom outer layer 38 could becorona-treated to allow permanent or removable marking thereon as notedabove. In addition, the resulting film may be laminated to anotherstructure, such as a substrate. Thus, as seen in FIG. 3, the materialcan be cut or severed to a desired size, mounted on a surface and usedas a portable dry-erase board. Marking of the material can be undertakenat any time, for example, before severing, after severing but beforemounting or after mounting.

Still further, the material 10 may be printed on one or more surfacesthereof. Also, the film material 10 may be perforated at one or morelocations 39 (FIG. 4) to permit tearing into sheets without the need fora cutter bar.

According to a further embodiment, the film material 10 is identical tothe embodiment illustrated in FIG. 4 except that the outer layers 36 and38 are omitted. In addition, the three layers are coextruded orlaminated and each layer comprises 187, 155LLG102 BOPP manufactured byExxon Mobil Corp., wherein the layers are not modified by pigment andare not cavitated to obtain a clear product.

If desired, the material 10 need not be electrically charged.

Industrial Applicability

The present invention is not limited to the concept of providing amaterial that may be used as noted above. For example, the material 10may be used to line one or more shelves 50 or drawers 52 (FIGS. 5 and 6)and items may be placed and/or processed thereon, or the material 10 maybe used to cover and/or protect the surfaces of other furniture,articles and other support surfaces so that one or more items may beplaced and/or processed thereon (such as house plants, picture frames orthe like). Items other than food, e.g., items used in crafts, may besupported on the material 10 for processing. Alternatively, the materialmay be used as a dropcloth and/or placemats or in another application,such as in a refrigerator or microwave, where protection of a supportsurface is desired. Still further, the material 10 may be used as acover for a bowl, cup or other receptacle, or may be used to serve as asplash guard for one or more surfaces in a microwave oven orrefrigerator, or may be used like masking tape to keep paint from beingapplied from areas that are to remain unpainted. Another use is toretain an item on place on a windowpane or other object by sandwichingthe object between the film material 10 and the windowpane or otherobject. The surface upon which the material 10 is placed may becontinuous or discontinuous (an example of the latter would be a tilefloor). In addition, the surface may be hard or soft, and need not havea homogenous composition or exhibit homogeneous physicalcharacteristics.

As further alternatives, the film material 10 may include one or moreopenings or apertures therethrough and/or the material 10 may includepigmented and non-pigmented areas and/or electrically-charged andnon-charged areas, as desired. Thus, for example, a rectangular piece offilm material 10 may include an outer portion comprising a frame whichis electrostatically charged and which is corona treated to acceptremovable or permanent marking thereon and a central portion which isclear or which has an opening therethrough. The material of the centralportion (if any) may be electrostatically charged or uncharged. Theresulting product is particularly suited to hold a photograph, drawing,painting, greeting card, or other object to a windowpane or othersubstrate (vertical or nonvertical) such that the photograph, drawing,etc . . . is visible through or at the central portion. In the case ofapplications where the film material 10 is to hold an object to avertical surface and where either portions of or the entire sheet(including any central portion) is electrically charged, the filmmaterial 10 preferably (although not necessarily) carries an electriccharge sufficient to enable the material to hold a weight of a separateobject at least equal to the weight of the film material 10. Inalternate embodiments, the charge is sufficient to allow the material tohold a weight of a separate object greater than the weight of the filmmaterial, for example, a weight at least equal to three times the weightof the film material.

According to still further alternative, a sheet of the film material 10may include outer margins that retain electric charge, such as anelectrostatic charge. The sheet may be folded on itself such thatportions of the outer margins are placed into contact with one another,thereby forming a pocket that may enclose an object. If desired, theentire sheet may carry an electric charge or portions of the sheet otherthan the margins may carry an electric charge. One or more surfaces mayoptionally be treated as noted above to permit permanent or removablemarking of such surface(s) by a marking device, such as a dry erasemarker. As in the previous embodiments, the film material prevents thetransmission of bacteria and fluids between the surfaces of thematerial.

Yet another embodiment of the present application comprehends anelectrically charged sheet of film material as described above inconnection with any of the previous embodiments, wherein the filmmaterial 10 is treated and/or modified in some fashion to apply adesired substance having a desired property thereto. For example, aquantity of electrostatically charged film having a surface that may betreated so as to be capable of being marked by a dry erase marker mayfurther have one or more portions coated with a volatile substance, suchas an insecticide, a bactericide, an antimicrobial agent and/or afragrance. The film may be liquid impermeable and may be trimmed to adesired size and placed in contact with a surface (such as a topsurface, undersurface or side surface of a shelf, table, drawer, etc . .. ) such that the film is attracted to and retained on the surface. Thesubstance thereafter volatilizes to release same into the ambientsurroundings. Optionally, an item may be processed on the film, providedthat the item is not adversely affected by the volatile substance.

If desired, the substance may be a substantially non-volatile liquid,such as an oil, or a solid material or article, such as a printed sheetof paper, fabric, plastic, etc . . . . In this case, the substance maybe irremovably secured to the film material 10, or the substance may beremovable therefrom. In the latter case, the film material 10 may serveas a transfer carrier that carries the substance until the film material10 is applied to a surface, whereupon the substance is transferred tothe surface and is retained thereon by any suitable mechanism. Suchmechanism may include electrostatic attraction resulting from electriccharge transferred to the substance by the film material 10. Analternative mechanism may comprise adhesion resulting from making one ormore surfaces of the substance sticky. In any event, the film material10 may be peeled from the surface, leaving at least some quantity of thesubstance on the surface.

Alternatively, a volatile material or other substance or article may beretained in or by a structure carried by or secured to the film. Forexample, as seen in FIGS. 7 and 8, a layer 60 of a first film may bedisposed atop and secured to a layer 62 of a second film that carries anelectric charge as noted above to create a pocket 64. The layers 60 and62 may be made of any of the materials described above or any othermaterial and the layer 60 may be secured to the layer 62 in any knownmanner, such as by heat sealing, adhesive bonding, coextrusion, or thelike. A pad 66 impregnated with a desired substance, such as afragrance, insecticide or any other substance as described herein, maybe disposed in the pocket 64. The pad 66 may comprise a gel disposed inan envelope formed by two layers of vapor permeable material that aresecured to one another by any suitable means. One or both of the layers60, 62 may be vapor permeable and/or one or more openings or apertures68 may be provided in the first and/or second films to permit vaporcommunication between the ambient surroundings and the pocket 64. Theholes 68 may initially be covered by one or more removable adhesivestrips 70 (shown only in FIG. 7) or other members. The resulting productmay be placed on any desired object at a desired position (including atop surface, side surface or an undersurface of the object) and isretained thereon by the electric charge carried by the film. Theadhesive strip(s) 70 may then be removed to expose the substance to theambient surroundings. The substance, if volatile, will thereafterevaporate and spread in vapor form to the surroundings. If desired, thepad 66 may be replaced by a different carrier, such as a fibrous pad orother material containing or impregnated with a desired substance.

A still further alternative is a design whereby a pouch is formed of amaterial (whether one of the materials described above or any othermaterial), either by folding the material upon itself or by securing twoor more pieces of the same or dissimilar materials together to form onemore pockets, and securing the pouch by any suitable means (e.g., heatsealing, adhesive, coextrusion, co-lamination or the like) to a sectionof a film that carries electric charge as described above. One or moreobjects may be disposed in the pocket(s), including a pad impregnatedwith a substance as described above. The material of the pouch may bevapor permeable an/or may include one or more openings extendingtherethrough. One or more holes covered by removable members may beprovided as in the preceding embodiment. The resulting product may beplaced and used as described in the preceding embodiment to expose theimpregnated substance to ambient surroundings.

In any of the foregoing embodiments, the desired substance may be arepellant and/or toxic to one or more undesirable organisms, creatures,etc . . . . Thus, the desired substance may comprise an antimicrobialcomposition, an insecticide, a bactericide, a herbicide, an animalrepellant, or the like. Alternatively, the desired substance may be anattractant (such as a fragrance as noted above) or a substance thatencourages growth or multiplication of one or more organisms. Ofparticular interest in this regard are scents and other air qualitycontrol active ingredients and insect control ingredients, includinginsecticides, repellants and other insect behavioral and/ordevelopmental modification ingredients. Any of these substances can beapplied to the film material 10 by any suitable means in addition tothose described above, such as a composition which is printed directlyon the film material 10, a woven or non-woven fabric or other materialimpregnated with the substance and laminated or otherwise joined to thematerial 10, etc . . . . The substance may therefore be dispensedwithout messy and/or sticky residue. One example of such a substancerelease arrangement is a 10 inch by 10 inch 2 mil polypropylene filmwith 100 milligrams of transfluthrin or other insecticide or activeapplied thereto. Other insecticidal compositions may instead be used inthis manner. The resulting material may be supplied in sheet or rollform, and in the latter case, the material may be torn or cut into adesired size by a cutter bar or other implement as described above. Thematerial may alternatively be perforated to allow ready separation intoindividual sheets, also as noted above. The material may be placed on asubstantially horizontal undersurface or any other surface of an object,such as a tray, table countertop, drawer, shelf, a substantiallyvertical surface, etc . . . , whereupon the volatile substancevolatilizes to release an active ingredient into the surroundingenvironment.

If desired, any of the foregoing embodiments may be adapted to beutilized with a heater that heats the film material 10 either toinitiate or accelerate the release of the substance into the surroundingatmosphere. A fan may instead or in addition be used toinitiate/accelerate substance release.

Yet another embodiment comprehends a structure including two or morecompartments or pockets secured to the electrically charged filmmaterial 10. For example, as seen in FIGS. 10 and 11, amulti-compartment arrangement 80 includes at least first and secondcompartments or pockets 82, 84 separated by a rupturable intermediatewall 86. The compartments 82, 84 are captured between a base layercomprising a section of the film material 10 and a cover layer 88 thatis secured by any suitable means to the base layer. In the case of astructure having more than two compartments, each compartment isseparated from adjacent compartment(s) by one or more rupturable walls.A chemical composition is disposed in each compartment and therupturable walls may be selectively ruptured by physical manipulation tomix the chemicals and thereby initiate a desired chemical reaction. Thestructure may be retained on any surface by the charge carried by thefilm material 10. Thus, for example, a cold pack may be provided by amulti-compartment structure wherein the components of the cold pack areseparated before use by rupturable walls. A user may rupture the wallswhen the cold pack is to be used such that the chemicals are mixed andthe chilling process is initiated, whereupon the cold pack may beapplied to an affected area of a person's body. The cold pack isadvantageously retained at the affected area by the charge carried bythe film material 10. Other similar arrangements can be envisionedwhereby chemicals are selectively mixed to produce heat, light, smoke orother byproduct, and the structure is retained on a surface by theelectric charge carried by the film material 10.

Any of the features of one of the embodiments disclosed above can becombined with one or more features of one or more other embodimentsdisclosed above. Thus, for example, an electrically charged sheet ofpolymer material as described above having the above-noted chargeretention and holding characteristics may be coated or impregnated witha volatile substance, such as an insecticide or fragrance, and, ifdesired, one or both surfaces of the sheet may be treated to permitpermanent or removable marking of such surface(s) by a marking device,such as a dry erase marker. The material may be supplied in sheet orroll form, and in the latter case, the material may be torn or cut intoa desired size by a cutter bar or other implement as described above.The material may alternatively be perforated to allow ready separationinto individual sheets, also as noted above.

Numerous modifications to the present invention will be apparent tothose skilled in the art in view of the foregoing description.Accordingly, this description is to be construed as illustrative onlyand is presented for the purpose of enabling those skilled in the art tomake and use the invention and to teach the best mode of carrying outsame. The exclusive rights to all modifications which come within thescope of the appended claims are reserved.

1. A method of producing an electrically charged film, the methodcomprising the steps of: forming a molten thermoplastic material into aweb; electrically charging the web while the web is at a temperatureabove a solidification temperature thereof; cooling the web below thesolidification temperature thereof after charging; winding the web intoindividual user rolls immediately following the cooling step; andplacing each individual user roll into a user box to obtain a pluralityof boxes of charged film rolls.
 2. The method of claim 1, wherein thecharge applied to the web during the step of charging results in a webthat retains sufficient charge to develop at least 1500 volts at threemonths following the step of charging.
 3. The method of claim 1, whereinthe charge applied to the web during the step of charging results in aweb that retains sufficient charge to develop at least 2500 volts. 4.The method of claim 1, wherein the charge applied to the web during thestep of charging results in a web that retains sufficient charge todevelop at least 3500 volts.
 5. The method of claim 4, wherein the stepof charging comprises the step of passing the web through anelectrostatic charging machine to electrostatically charge the web. 6.The method of claim 5, wherein the electrostatic charging machineapplies an electric field of greater than 25,000 volts to the web. 7.The method of claim 6, wherein the electrostatic charging machineapplies the electric field at an approximate distance of between ½ inchand 1 inch.
 8. The method of claim 6, wherein the electrostatic chargingmachine applies the electric field at an approximate distance of ¾ inch.9. The method of claim 6, wherein the electrostatic charging machineapplies an electric field substantially greater than 25,000 volts to theweb.
 10. The method of claim 9, wherein the electrostatic chargingmachine applies the electric field at an approximate distance of between½ inch and 1 inch.
 11. The method of claim 9, wherein the electrostaticcharging machine applies the electric field at an approximate distanceof ¾ inch.
 12. The method of claim 9, wherein the electrostatic chargingmachine applies an electric field of at least approximately 30,000 voltsto the web.
 13. The method of claim 12, wherein the electrostaticcharging machine applies the electric field at an approximate distanceof between ½ inch and 1 inch.
 14. The method of claim 12, wherein theelectrostatic charging machine applies the electric field at anapproximate distance of ¾ inch.
 15. The method of claim 1, wherein thecharge applied to the web during the step of charging results in a webhaving a moderate to high resistance to shear forces but which can bereadily peeled from a surface.
 16. The method of claim 1, wherein thestep of forming comprises the step of extruding the thermoplasticmaterial.
 17. A method of producing an electrically charged film, themethod comprising the steps of: extruding a molten thermoplasticmaterial into a web, wherein the web includes a surface adapted formarking by a marking device; electrically charging the web while the webis at a temperature above a solidification temperature thereof; coolingthe web below the solidification temperature thereof after charging; andwinding the web onto one of a plurality of rolls disposed on a rotatableturret immediately following the cooling step; wherein the step ofcharging results in a web having a moderate to high resistance to shearforces but which can be readily peeled from a surface.
 18. The method ofclaim 17, wherein the charge applied to the web during the step ofcharging results in a web that retains sufficient charge to develop atleast 1500 volts at three months following the step of charging.
 19. Themethod of claim 17, wherein the charge applied to the web during thestep of charging results in a web that retains sufficient charge todevelop at least 2500 volts.
 20. The method of claim 17, wherein thecharge applied to the web during the step of charging results in a webthat retains sufficient charge to develop at least 3500 volts.
 21. Themethod of claim 20, wherein the step of charging comprises the step ofpassing the web through an electrostatic charging machine toelectrostatically charge the web.
 22. The method of claim 21, whereinthe electrostatic charging machine applies an electric field of greaterthan 25,000 volts to the web.
 23. The method of claim 22, wherein theelectrostatic charging machine applies the electric field at anapproximate distance of between ½ inch and 1 inch.
 24. The method ofclaim 22, wherein the electrostatic charging machine applies theelectric field at an approximate distance of ¾ inch.
 25. The method ofclaim 22, wherein the electrostatic charging machine applies an electricfield of substantially greater than 25,000 volts to the web.
 26. Themethod of claim 25, wherein the electrostatic charging machine appliesthe electric field at an approximate distance of between ½ inch and 1inch.
 27. The method of claim 25, wherein the electrostatic chargingmachine applies the electric field at an approximate distance of ¾ inch.28. The method of claim 25, wherein the electrostatic charging machineapplies an electric field of at least approximately 30,000 volts to theweb.
 29. The method of claim 28, wherein the electrostatic chargingmachine applies the electric field at an approximate distance of between½ inch and 1 inch.
 30. The method of claim 28, wherein the electrostaticcharging machine applies the electric field at an approximate distanceof ¾ inch.
 31. The method of claim 17, wherein the charge applied to theweb during the step of charging results in a web having a moderate tohigh resistance to shear forces but which can be readily peeled from asurface.
 32. The method of claim 17, wherein the step of formingcomprises the step of extruding the thermoplastic material.